This invention relates to a control for a marine transmission and more particularly to an improved actuator assembly for such transmissions.
Conventional marine transmissions employ a driveshaft which has a bevel gear that is affixed to its lower end and which is engaged with a pair of diametrically opposed, and hence, counter-rotating-driven beveled gears. This driven bevel gears are journaled on the propeller shaft and are selectively clutched for driving relationship therewith by a dog-clutching mechanism that is positioned between the bevel gears.
It is conventional to utilize a shift plunger which extends into one end of the propeller shaft and which operates in conjunction with a pin that carries the dogclutching element for effecting the axial shifting of the dog-clutching element into engagement with selected ones of the driven counter-rotating bevel gears.
Various types of mechanisms have been employed for actuating the shift plunger. Some of these utilize a cam mechanism that is operated by a rotating cam formed at the lower end of a shift rod which is actuated by the vessel operator. This cam mechanism requires the cam to be held against rotation about the propeller shaft axis while the shift plunger does rotate along with the pin that couples it to the dog-clutching element. Hence, a number of small pieces must be assembled together in order to complete this mechanism. This adds to the cost and complexity and also gives an area where failures may occur.
Another type of mechanism employs a crank pin that operates in a slot in the shift plunger. This eliminates the need for the connecting member to permit relative rotation. However, these types of mechanisms require a fairly large bearing area and generally make it difficult to keep a small size for the lower unit. If the lower unit's size is increased, particularly at its forward end where this mechanism resides, then hydrodynamic drag can be unacceptably increased.
It is, therefore, a principal object of this invention to provide an improved transmission control for a marine transmission reversing-gear shifting mechanism.
It is a further object of this invention to provide an improved actuating mechanism for the shift plunger of a marine transmission that can be relatively small in operation and size, can be conveniently assembled, and also will have a relatively large bearing area.